A conventional air conditioning system provided in a building generally has an air compressor driven by a motor powered by a municipal utility electricity. It will cause an energy conversion loss because the electrical energy must be first converted to a mechanical energy to drive the motor and the air compressor. When a power failure occurs, a standby power generator driven by a diesel engine is started to continuously supply electricity to the motor for driving such a compressor, which still causes energy conversion loss.
It is therefore expected to have an energy-saving system capably recovering the waste heat energy from an air conditioning system having an air compressor directly coupled to and driven by an internal combustion engine.